Solenoid housings are typically used in car control systems, such as doors, windows, hydraulic controls, engine control, and the like. Other uses include refrigerators, washers, and dryers. Further uses include electrically actuated valves/switches, door holders, speakers, and CRT monitors.
A solenoid housing is typically assembled in parts, where center pole 8 is welded or attached in any fashion to cup 12 shown in FIGS. 1a-1b, where cup 12 is usually cut from sheet metal and bent to the shape shown. Cup 12 usually starts as a flat disc cut from sheet metal and is bent upwardly around the perimeter of the disc to define a raised wall 14, or a raised lip, extending around the perimeter. Base 16 of the disc, or the part of the disc remaining flat, is usually welded or attached to pole 8.
Another way of making a solenoid housing may be to machine the various pieces in addition to or instead of assembly the pieces together. Some methods include machining at least a part of the cup or pole.
However, making a solenoid housing in the manners described above presents several disadvantages. When assembling the parts together, such as welding pole 8 to base 16, a weak point may be introduced and any mechanical failure is usually located at the junction between pole 8 and base 16.
In addition, since an electromagnetic field typically flows from pole 8 to base 16 and ultimately to raised wall 14, a bottle neck frequently occurs at the juncture of base 16 and pole 8 because base 16 is of sheet metal and its thinness provides a small cross section through which the electromagnetic field may flow. As a consequence, even though pole 8 may have a large diameter to originally permit the electromagnetic field to enter and pass downwardly toward base 16, such electromagnetic field will ordinarily be impeded once the electromagnetic field is transferred from pole 8 to base 16 on its way toward raised wall 16.
Further, one can argue the orientation of the grain structure of base 16 and raised wall 14 inhibits the flow of the electromagnetic field because the grain structure may be perpendicular or angular relative to the radially traveling electromagnetic field. Since cup 12 is usually cut from sheet metal, the orientation of the grain structure is usually not known and often is not predictable or adjustable.
With regard to machining parts of cup 12 or pole 8, such practice is normally labor intensive and usually time consuming because no more than several thousandths or hundredths of an inch may be removed at a time, and removing material at this rate often translates to long periods of time for producing a solenoid. Moreover, the lathes used for machining parts are often expensive and require a large amount of space for proper operation. Therefore, any benefits obtained from machining parts over assembling parts may be outweighed by the associated costs.
U.S. Pat. No. 4,217,567 appears in FIGS. 10 and 10A to relate to a simple soft iron plug or insert 75 with a conforming nose portion pressed as an interference fit into the external hollow space formed by the inwardly extending pole portion 52. The plug 75 has the effect of increasing the flux-carrying capacity across the gap defined by the wall 60 of the bobbin 55. Substantially the same effect may be achieved, at still lower cost, in which the flux carrying plug means comprises one or more mild steel balls 76 pressed into the hollow external cavity defined by the pole portion 52.
U.S. Pat. No. 6,029,704 Kuroda et al. appears to disclose a press formed or cold forged steel plate and a hollow cylindrical solenoid. However, because Kuroda's solenoid housing and pole is made from multiple parts and assembled, it does not efficiently conduct the electromagnetic field.
U.S. Pat. No. 4,365,223 to Fechant et al. relates to a solenoid housing that may be put together in pieces.
What is desired, therefore, is a method of making a solenoid housing that reduces weak points without sacrificing manufacturing efficiency. Another desire is a method of making a solenoid housing that enhances a flow of an electromagnetic field.